Francis-type runner

ABSTRACT

The length of the entrance edge of each blade on the side of the crown ring is made longer than that on the side of the shroud ring; and the runner satisfies the following three conditions: 15 DEG &lt;/= theta &lt;/=35 DEG  gamma 1c&lt;/= gamma 1s D1 c&lt;/= D1s WHERE  theta  = AN ANGLE BETWEEN THE CENTERLINE OF THE RUNNER AND A LINE CONNECTING THE POINTS AT WHICH THE ENTRANCE EDGE OF THE BLADE CONTACTS WITH THE CROWN AND SHROUD RINGS RESPECTIVELY;  gamma 1 C = AN ANGLE BETWEEN THE LINE PASSING THROUGH THE CENTER OF THE RUNNER AND A POINT AT WHICH THE ENTRANCE EDGE OF THE BLADE CONTACTS WITH THE CROWN RING AND THE NORMAL TO THE TANGENT AT SAID CONTACT POINT TO THE CURVED SURFACE OF THE BLADE;  gamma 1S = AN ANGLE BETWEEN THE LINE PASSING THROUGH THE CENTER OF THE RUNNER AND A POINT AT WHICH THE ENTRANCE EDGE OF THE BLADE CONTACTS WITH THE SHROUD RING AND THE NORMAL TO THE TANGENT AT SAID CONTACT POINT TO THE CURVED SURFACE OF THE BLADE; D1c = an outer diameter of the blade at a point where the blade contacts with the crown ring; and D1s = an outer diameter of the blade at a point where the blade contacts with the shroud ring.

United States Patent Yamahe [54] FRANCIS-TYPE RUNNER [72] inventor: Masahiro Yamabe, Hitachi, Japan [73] Assignee: Hitachi, Ltd'., Tokyo, Japan [22] Filed: Oct. 26, 1970 [21] Appl. No.: 84,078

[52] U.S.Cl ..4l6/186,416/188 [51] Int. Cl ..F0ld 5/04 [581 FieldotSearch ..416/186,181,185, 179,213 A, 416/241 A, 187,183,192, 188

[56] References Cited UNITED STATES PATENTS 3,224,078 12/1965 Mayne ..4l6/l86 3,224,079 12/1965 Dybvig ..416/186 FOREIGN PATENTS OR APPLICATIONS 691,676 3/1930 France ..416/186 Primary Examiner-Edgar W. Geoghegan Assistant ExaminerClemens Schimikowski Attorney-Craig, Antonelli, Stewart & Hill 1 1 Feb. 1, 1972 [5 7] ABSTRACT V The length of the entrance edge of each blade on the side of the crown ring is made longer than that on the side of the shroud ring; and the runner satisfies the ll'ollowing three condi- 1101182 '5 s 350 .yll s where D G 2 D S 9 an angle between the centerline of the runner and a line connecting the points at which the entrance edge of the blade contacts with the crown and shroud rings respectively;

-y c= an angle between the line passing through the center of the runner and a point at which the entrance edge of the blade contacts with the crown ring and the normal to the tangent at said contact point to the curved surface of the blade;

y,s an angle between the line passing through the center of the runner and a point at which the entrance edge of the blade contacts with the shroud ring and the normal to the tangent at said contact point to the curved surface of the blade;

D c= an outer diameter of the blade at a point where the blade contacts with the crown ring; and

D s= an outer diameter of the blade at a point where the blade contacts with the shroud ring.

1 Claims, 5 Drawing Figures PATENTED FEB I I972 F/G. lb

F/G. la

INVENTOR OPEN/N6 0F GU/DEl/A/VE M QQQQR int 3: KQ RBDRDQ MASAHI HO YAMA BE RPM CY Ej skewed.

ATTORNEYS FRANCIS-TYPE RUNNER BACKGROUND OF THE INVENTION The present invention relates to a Francis-type turbine and more specifically a Francis-type runner. More particularly the present invention relates to the contour of the entrance of a Francis-type runner.

In general, a Francis-type runner comprises a crown ring, a shroud ring and a plurality of blades between them. The efficiency of a turbine employing such Francis-type runner does not correspond to the designed effieiency in some cases so that the operation control of the turbine is much adversely affected.

SUMMARY OF THE INVENTION The present invention was made to overcome this problem. In brief, the present invention provides an improved Francistype runner in which the length of the entrance edge of the blade on the side of the crown ring is made longer than that on the side of the shroud ring; and the Francis-type runner is designed to satisfy the following relations:

where an angle between the centerline of the runner and a line connecting the points at which the entrance edge of the blade contacts with the crown and shroud rings respectivcly;

y c an angle between the line passing through the center of the runner and a point at which the entrance edge of the blade contacts with the crown ring and normal to the tangent at said contact point to the curved surface of the blade;

032 an angle between the line passing through the center of the runner and a point at which the entrance edge of the blade contacts with the shroud ring and the normal to the tangent at said contact point to the curved surface of the blade;

0,0 an outer diameter of the blade at a point where the blade contacts with the crown ring; and

l),s an outer diameter of the blade at a point where the blade contacts with the shroud ring.

The present invention will become more apparent from the following description of the preferred embodiment thereof taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE INVENTION FIG. la is a fragmentary sectional view of a Francis-type runner in accordance with the present invention;

FIG. Ibis a side view thereof;

FIG. lc is a horizontal sectional view thereof;

FIG. 2 is a graph illustrating the effieiency of a Franeis-type runner vs. the speed; and

FIG. 3 is a graph illustrating the output thereof vs. the guide vane opening.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 2 illustrates a test result of a Francis-type turbine in which the efficiency is plotted against the speed for each of several guide vane openings. It is seen that the turbine has two efficiency curves at each one of guide vane openings G G within certain ranges of the speed. This will be described in more detail with reference to the curve for the guide vane opening G... When the speed n is gradually increased from the point a on the curve G the efficiency curve suddenly changes from the point b on the high-efficiency curve to the point r: on the low-efficiency curve. When the turbine speed is increased or decreased between the points d and e, the efficiency is gradually increased or decreased accordingly, but when the point e is reached, the efficiency suddenly changes from the point e on the Iow-efficiency curve to the pointf on the highfrequency curve.

In FIG. 3 the output of the turbine at the speed m in FIG. 2 is plotted against the guide vane opening. These phenomena are observed also in the field units.

The cause of these phenomena is that the flowing water is separated from the runner blades on the side of the crown ring at the runner entrance so that the swirls are superposed upon each other in the passage defined by the runner blades, crown ring and the shroud ring. Because of these swirls the flow rate or the work done by the runner is changed so that the turbine exhibits a high efficiency in some cases or low efficiency in other cases.

These swirls are caused by the contour of the runner entrance. Therefore, it is desired to change the contour of the runner entrance in such a manner that the entering flow will not be separated from the runner blades at the entrance. The extensive experiments conducted by the inventor showed that the blade entrance angle 6 indicated in FIG. lb is an important factor in design. The angle 6 is an angle between the centerline of the runner and the line connecting the points x and y where entrance edge of the blade 3 contacts with the crown ring and the shroud ring respectively. It is seen that the point x is located left relative to the point y, that is the length of the blade 3 on the side of the crown ring is longer than that on the side of the shroud ring 2. It should be noted that the point x is the vertex of the angle 6. The experiments showed that the angle between 15 and 35 is effective for preventing the swirls.

In addition, it was found out that the following relation must be satisfied:

D,c D s where D c an outer diameter of the blade at a point where it makes contact with the crown ring; and D s an outer diameter of the blade at a point where it makes contact with the shroud ring. Furthermore, it is more advantageous to satisfy the following condition: 71 Yr where y c an angle between the line passing through the center of the runner and a point at which the entrance edge of the blade contacts with the crown ring and the normal to the tangent at said contact point to the curved surface of the blade; and

'y,s an angle between the line passing through the center of the runner and a point at which the entrance edge of the blade contacts with the shroud ring and the normal to the tangent at said contact point to the curved surface of the blade. In the conventional runner, 6 l5 while 'y s 'y c so that the flow is easily separated from the blade.

According to the present invention, when the abovedescribed conditions 15 0 35 D c D, and

71 71 are satisfied, the swirls may be prevented in the passage so that the designed efficiency having no double-efficiency-curve" may be attained.

What is claimed is:

I. Francis-type runner comprising a crown ring, a shroud ring and a plurality of blades interconnected therebetween, in which the length of the entrance edge of each blade on the side of said crown ring is longer than that on the side of said shroud ring; and said runner satisfies the following relations:

'Yi Yr D c D s where 0 an angle between the center line of said runner and a line connecting the points at which the entrance edge of said each blade contacts with said crown ring and said shroud ring respectively;

normal to the tangent at said contact point to the curved surface of said each blade;

D,c= an outer diameter of said each blade at a point where said each blade contacts with said crown ring; and

D,s an outer diameter of said each blade at a point where said each blade contacts with said shroud ring.

UNITED (STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,639,080 Dated February 1, 1972 Inventor(s) Masahiro Yamabe It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Title Page, left column, line 15, which now reads:

"691, 676 3/1930 France. .416/186" should read as follows:

-October 27, 1969 v Japan. 85244/69- Signed and sealed this 11th day of July 1972.

(SEAL) Attest:

EDWARD M. FLET CHER, JR R0 BERT GOTT SC HAL K Atte stin g Offic er Commi ss ioner of Paten ts FORM PO-lOSO (10-69) USCOMM-DC 60376-P89 a u.s GOVERNMENT PRINTING OFFICE I969 o--3ss-a:4 

1. Francis-type runner comprising a crown ring, a shroud ring and a plurality of blades interconnected therebetween, in which the length of the entrance edge of each blade on the side of said crown ring is longer than that on the side of said shroud ring; and said runner satisfies the following relations: 15* < OR = theta < OR = 35* gamma 1c < OR = gamma 1s D1c < OR = D1s where theta an angle between the center line of said runner and a line connecting the points at which the entrance edge of said each blade contacts with said crown ring and said shroud ring respectively; gamma 1c an angle between the line passing through the center of said runner and a point at which the entrance edge of said each blade contacts with said crown ring and the normal to the tangent at said contact point to the curved surface of said each blade; gamma 1s an angle between the line passing through the center of said runner and a point at which the entrance edge of said each blade contacts with said shroud ring and the normal to the tangent at said contact point to the curved surface of said each blade; D1c an outer diameter of said each blade at a point where said each blade contacts with said crown ring; and D1s an outer diameter of said each blade at a point where said each blade contacts with said shroud ring. 